KR20000048535A - Process for the preparation of substituted aromatic amino compounds - Google Patents

Abstract

PURPOSE: Provided is a hydrogenation process for the preparation of aromatic amino compounds containing directly on the aryl ring or in a side chain one or more entities that may also undergo hydrogenation, such as carbon multiple bonds, nitrile groups, imino groups or carbonyl groups. CONSTITUTION: Provided is a process for the preparation of substituted aromatic amino compounds containing at least one carbon-carbon, carbon-nitrogen or carbon-oxygen multiple bond on the aromatic moiety or in a side chain, by means of catalytic hydrogenation of corresponding substituted aromatic nitro compounds in the presence of a modified noble metal catalyst, wherein rhodium, ruthenium, iridium, platinum or palladium modified with an inorganic or organic phosphorus compound having an oxidation state of less than 5 is used as the noble metal catalyst.

Description

Process for the preparation of substituted aromatic amino compounds

The present invention provides hydrogenation for preparing aromatic amino compounds that directly contain one or more residues, such as carbon multiple bonds, nitrile groups, imino groups or carbonyl groups, which may also undergo hydrogenation in the aryl ring or side chain. It is about a method. This method of preparation is carried out by catalytic hydrogenation of the corresponding aromatic nitro compounds in the presence of phosphorus-modified noble metal catalysts. The present invention also relates to the use of modified noble metal catalysts for hydrogenating aromatic nitro compounds containing carbon multiple bonds and / or substituted by nitrile, imino or carbonyl groups.

It is known that aromatic nitro compounds can be reduced in the presence of noble metal catalysts and hydrogen to give aromatic amines in very good yields. If additional hydrogenable groups, such as carbon multiple bonds, nitrile, imino or carbonyl groups, are present at the same time, special measures are necessary to prevent the formation of undesirable secondary products, and In these cases, these secondary products can sometimes be separated from the desired product only by resource-intensive methods, but in particularly disadvantageous cases these products cannot be separated at all. If several hydrogenable groups are present in one compound, it is particularly difficult to selectively reduce them.

Numerous methods have been proposed in the prior art to selectively reduce aromatic nitro compounds substituted by hydrogenable groups. For example, WO 95/32941 and WO 95/32952 describe methods for hydrogenating aromatic nitro compounds substituted by one or more groups with carbon multiple bonds. Precious metal catalysts modified with lead, mercury, bismuth, germanium, cadmium, arsenic, antimony, silver or gold have been proposed as catalysts. Although these catalysts are in principle very suitable and can be used for large scale production, they are sometimes disadvantageous in terms of their activity and selectivity.

US-A-4 020 107 discloses phosphoric acid, hypophosphoric acid or derivatives thereof when the halo-substituted aromatic nitro compound on an aromatic moiety is hydrogenated with Pt or Pd / active carbon and hydrogen. It is proposed to use as.

Although these systems are selective for halogen substituents present in the molecule, they often exhibit limited reactivity. Thus, in many cases, it is observed that a significant amount of aryl hydroxylamine is formed. See J.R. Kosak, in Catalysis of Organic Reactions, Vol. 18 (1988), 135-147; idem, in Catalysis in Organic Synthesis, 1980, 107-117].

The catalytic hydrogenation of aromatic nitro compounds to the corresponding aromatic amines proceeds through several intermediates. See, eg, literature; As described in M. Freifelder, in Handbook of Practical Catalytic Hydrogenation, published by Wiley-Interscience, New York, 1971, the corresponding nitroso compounds and especially hydroxylamine intermediates are important in this document.

These hydroxylamine intermediates pose certain problems in practical use because they can accumulate in large amounts in the reaction solution under certain conditions. This is particularly the case with aromatic nitro compounds, and the hydrogenation of such compounds produces relatively stable aryl hydroxylamines, which is particularly problematic when the hydrogenation of the compounds is carried out in slurry batch reactors. In extreme cases, tons of aryl hydroxylamines can be formed in this manner.

Accumulation of aryl hydroxylamine is undesirable in many respects. For example, it is known that such compounds are often thermally unstable and can undergo a disproportionation reaction with significant heat release when heated in the presence or absence of H ₂ . The heat released in this way can lead to further decomposition reactions, which in turn can lead to events involving severe explosions. See WR Tong et al., AICHE Loss Prev. 1977, (11), 71-75, describe this event in reducing 3,4-dichloro nitrobenzene to 3,4-dichloroaniline.

Because of this instability, detailed and resource-intensive thermal studies of indispensable hydrogenation mixtures should be conducted before starting production. In particular, the thermal characteristics of potential hydroxylamine intermediates must be thoroughly studied. See F. Steoessel, J. Loss Prev. Process Ind., 1993, Vol. 6, No. 2, 79-85, describe a procedure using the example of hydrogenating nitrobenzene to aniline.

Moreover, aryl hydroxylamines are known to be potent carcinogens and therefore pose significant potential risks in the event of discontinuous or incomplete hydrogenation reactions [see; J.A. Miller, Cancer Res. 3 (1970), 559.

The third problem is that pure amines are produced. If a significant amount of aryl hydroxylamine is present during hydrogenation or at the end of the reaction, it may form a fusion with undesirable colored azo or azoxy products. Since the amount of aryl hydroxylamine may differ from batch to batch, product qualities varying in purity and appearance are obtained.

The problems mentioned so far are even more serious, due to the fact that even for the well-known and widely studied methods, the concentration of hydroxylamine intermediates formed, as well as their maximum possible concentration, cannot be predicted at all. Due to the presence of trace impurities, spontaneous accumulation of hydroxylamine intermediates can be caused in an unexpected manner. See, eg, JR Kosak, Catalysis of Organic Reactions, Vol. 18 (1988), 135 describes how addition of only 1% NaNO ₃ increases the accumulation from the initial <5% to about 30% during the hydrogenation of 3,4-dichloronitrobenzene.

Surprisingly, the catalytic hydrogenation process of an aromatic nitro compound directly containing at least one moiety, for example a carbon multiple bond, a nitrile group, an imino group or a carbonyl group, in the aryl ring or the side chain can also be hydrogenated. It has been found by the present invention that it can optionally be carried out when using rhodium, ruthenium, iridium, platinum or palladium catalysts modified with inorganic or organophosphorus compounds with an oxidation state of less than 5.

Unexpectedly, these catalyst systems can be used to selectively reduce aromatic nitro compounds to the corresponding amino compounds without simultaneously hydrogenating the unsaturated carbon, —CN, or —CO bonds of the substituents on the aromatic nitro compounds. Turned out.

Surprisingly, in many cases only low concentrations of hydroxylamine are formed. However, when a relatively large amount of hydroxylamine is expected, hydroxylamine formation can be substantially completely suppressed by adding a catalytic amount of promoter, for example a vanadium compound. Typically, a hydroxylamine concentration of less than 1% is observed. As a result, it becomes possible to use relatively high concentrations of aromatic nitro compounds, making it possible to carry out the hydrogenation process in a fairly economical manner.

The activity and selectivity of such catalyst systems is high, especially in the case of very sensitive compounds, for example propargyl nitrobenzoate.

Since the catalyst system is well known and can be easily produced from commercially available standard noble metal catalysts such as standard Pt or Pd catalysts, the catalyst quality is ensured at a constant level, which is important for large scale production.

Since no further heavy metal compound is required for the modification, there is also no possibility that the final product will be contaminated with heavy metals.

It is often possible to use low pressure (about 5 bar) and relatively low temperature (about 100 ° C.) in this hydrogenation process.

A further advantage of the process over known reduction methods, such as Bechamp or sulfide reduction, lies in the fact that no Fe sludge and acidic or sulfur-containing wastewater have to be disposed of. High purity products are obtained because substantially no azo or azoxy compounds are formed and the reaction can be carried out in conventional reactors without the use of specific materials. The hydrogenation reaction, in particular the terminating phase, proceeds rapidly. As a result, significant advantages are obtained in that the product quality is constant and economically.

The process has a high degree of operational reliability since hydroxylamine formation can be substantially suppressed by the addition of a promoter as needed.

The present invention provides a process for the carbonization of aromatic residues or side chains by catalytic hydrogenation of corresponding substituted aromatic nitro compounds in the presence of noble metal catalysts of rhodium, ruthenium, iridium, platinum or palladium modified with inorganic or organic phosphorus compounds having an oxidation state of less than 5 -A process for preparing substituted aromatic amino compounds containing at least one carbon, carbon-nitrogen or carbon-oxygen multiple bond. The precious metal catalyst used is preferably platinum or palladium, in particular platinum.

The precious metal catalyst is preferably used in an amount of 0.1 to 10% by weight, in particular 0.5 to 2% by weight, based on the aromatic nitro compound used.

Preference is given to using noble metal catalysts containing from 1 to 10% by weight of platinum. Platinum suitable for this modification may be used in platinum black, platinum oxide form, or preferably in metallic or oxidized form applied to a carrier. Particularly suitable carriers are silicon dioxide, aluminum oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate, titanium oxide, magnesium oxide, iron oxide, lead oxide, lead sulfate and lead carbonate in the form of activated carbon, silicic acid or silica gel. Carbon, aluminum oxide and silicon dioxide are particularly preferred. Platinum applied to the above mentioned carrier materials is commercially available or can be prepared according to methods familiar to those skilled in the art, as described, for example, in DE-OS-2 042 368.

In principle, inorganic or organic phosphorus compounds in which the oxidation state of phosphorus is less than 5 can also be used as modifiers. Examples of phosphoric acid derivatives are mentioned in US Pat. No. 4,020,107.

Examples of suitable further phosphorus compounds according to the invention include phosphine P (R _a ) _3-n (H) _n , phosphite P (OR _a ) ₃ , phosphinoic acid HO-P (H) _m (R _a ) _2-m , phosphine oxide O = P (R _a ) _3-n (H) _n , hypophosphonoic acid And , Hypophosphoric acid O = P (OH) (H) _m (R _a ) _2-m and phosphoric acid O = P (OH) ₂ H and O = P (OH) ₂ R _a [where R _a is a straight or branched chain C ₁ -C ₁₂ alkyl, C ₆ -C ₁₆ aryl or C ₄ -C ₁₆ heteroaryl, m is 0, 1 or 2 and n is 0, 1, 2 or 3;

Examples of C ₁ -C ₁₂ alkyl are various isomers of methyl, ethyl and propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl.

C ₆ -C ₁₆ aryl can be unsubstituted or substituted phenyl, naphthyl, anthracyl, 1,2,3,4-tetrahydronaphthalene, indene, azulene or biphenyl.

C ₄ -C ₁₆ heteroaryl is, for example, unsubstituted or substituted quinoline, isoquinoline, pyridine, pyrimidine, pyrazine, indole, thiazole, pyrazole, oxazole, imidazole or fluorenone.

R _a is preferably C ₁ -C ₆ alkyl, or phenyl, unsubstituted or substituted by C ₁ -C ₆ alkyl or C ₁ -C ₆ alkoxy.

Phosphorus compounds may be present in the form of free acids, salts, esters or amides so long as they are acids.

Diphenylphosphine, triphenylphosphine, phosphinoic acid and salts, amides and esters thereof, diphenylphosphinic acid, diphenylphosphite, phosphine oxide, phosphoric acid and salts and esters thereof, hypophosphoric acid and salts thereof, amides and Ester is preferred.

Particular preference is given to phosphoric acid and its salts, amides and esters, and hypophosphoric acid and its salts, amides and esters.

As salts, those having cations or ammonium cations from alkali metal and alkaline earth metal groups are preferably mentioned.

Preferred alkali and alkaline earth metals are Li, Na, K, Ca and Mg.

The ammonium cation may be an ammonium cation substituted by NH ₄ ⁺ , (C ₁ -C ₆ alkyl) ₄ N ⁺ , or a mixture of H and C ₁ -C ₆ alkyl.

Examples of C ₁ -C ₆ alkyl are various isomers of methyl, ethyl, and propyl, butyl, pentyl and hexyl.

The modification of the noble metal catalyst can in principle be carried out during the production process of the hydrogenation catalyst or in a subsequent process thereof. Preferably, however, it is carried out directly before the catalyst is added to the reaction mixture, or directly in the reaction mixture by separately adding the phosphorus compounds in dissolved or dispersed form and then stirring both components together with the solution to be hydrogenated. It is also possible to adjust the pH of the catalyst mixture to a specific value by adding acid or base during the reforming process. Likewise, it is possible to modify the noble metal catalyst using the phosphorus compound by first mixing the noble metal catalyst and the phosphorus compound together as a solid, or by dissolving the phosphorus compound in a solvent, slurrying the noble metal catalyst with the solution and then filtering it. . The catalyst thus modified can be stored and added to the solution to be hydrogenated as necessary.

Preferably, the modification of the noble metal catalyst with the phosphorus compound is carried out before the catalytic hydrogenation process.

Such phosphorus compounds may be soluble or dispersed in the reaction medium to be hydrogenated.

The ratio of the noble metal catalyst to the phosphorus compound for reforming is preferably 1: 0.1 to 1: 1000, in particular 1: 5 to 1: 200 parts by weight.

In a preferred embodiment of the process, a catalytic amount of promoter is additionally added. In many cases where accumulation of aryl hydroxylamine is expected, the addition of a promoter can effectively prevent this accumulation.

Suitable promoters are transition metal ions that are purely inorganic or optionally bound in complex with organic ligands. Such promoters may be dissolved in the reaction medium or may be applied to the carrier material, catalyst or modified catalyst.

Preferred transition metal ions are Fe ²⁺ , Fe ³⁺ , Ru ³⁺ , Mn ²⁺ , Mn ³⁺ , Co ²⁺ , Co ³⁺ , and vanadium compounds, where vanadium is in oxidized state 0, II, III, IV Or V).

Particular preference is given to elemental vanadium or vanadium compounds in which the oxidation state of vanadium is 0, II, III, IV or V.

The promoter can be dissolved or dispersed in catalytic amounts in the reaction medium.

In another preferred embodiment of the process, the vanadium compound is mixed with or applied to the noble metal catalyst. Such noble metal catalysts may have already been modified with a phosphorus compound or may only be modified with the phosphorus compound continuously. Such vanadium compounds can in principle be applied to the hydrogenation catalyst before or after the process of reforming to the phosphorus compound, during the process of their preparation.

It is also preferred to first apply the vanadium compound to a suitable carrier material and then to disperse it in the reaction medium. Suitable carrier materials are, for example, all carrier materials used in the preparation of commercially available powdered hydrogenation catalysts, as mentioned above. Activated carbon is particularly suitable.

Application to the catalyst or carrier material is carried out by a simple method, for example by dissolving the vanadium compound, slurrying the catalyst or carrier material in solution and then filtering.

During application of the vanadium compound, the pH of the slurry is adjusted to the desired value as needed by addition of an acid or base.

If the vanadium compounds are not soluble in the reaction medium, they can be mixed with the slurried catalyst in dispersed and slurried form and then filtered together.

Suitable vanadium compounds having oxidation states 0, II, III, IV or V are elemental vanadium and purely inorganic compounds, and organic complexes with, for example, oxalate and acetylacetonate.

Compounds in the form of hydrates of V ₂ O ₅ , V ₂ O ₄ , vanadium (III) acetyl-acetonate, vanadium (IV) oxyacetylacetonate, and purely inorganic salts, oxo salts or purely inorganic salts or oxo salts Vanadium compounds, such as these, are preferable. Examples thereof are VOCl ₃ , VCl ₆ ⁻ , [VO (SCN) ₄ ] ^2- , VOSO ₄ , NH ₄ VO ₃ , VCl ₃ , VOCl, VCl ₂ , and the corresponding halides with F or Br. Such compounds exist in various forms of hydrates depending on the pH value in aqueous solution (FA Cotton, G. Wilkinson, Anorganische Chemie, Verlag Chemie Weinheim 1968, 2nd edition, pages 757-766).

Preference is given to vanadate or vanadate hydrates with oxidation state V, vanadium (III) acetylacetonate and vanadium (IV) oxyacetylacetonate, in particular vanadium (III) acetylacetonate and vanadium (IV) oxyacetylacetonate Is preferred.

Of these vanadates, ammonium, lithium, sodium or potassium vanadate, and hydrates of these vanadates are preferred.

The vanadium compound is preferably used in an amount of 1 to 2000 ppm, in particular 5 to 1000 ppm, based on the aromatic nitro compound to be hydrogenated.

The weight ratio of vanadium compound to noble metal catalyst is preferably 1: 1 to 1: 10,000, in particular 1:10 to 1: 1000, more particularly 1:50 to 1: 750.

The process according to the invention is preferably carried out at a pressure of 1 to 100 bar, more preferably 1 to 40 bar, in particular 1 to 5 bar.

The temperature may be 0 to + 160 ° C, preferably +20 to +140, in particular +20 to + 100 ° C.

If the compound to be hydrogenated is liquid at the reaction temperature, the hydrogenation process can be carried out in the absence of a solvent, or if the resulting amino compound is liquid under reaction conditions, it can be used as a solvent.

However, it is also possible to add a solvent. Suitable solvents include, for example, water; Various isomers of alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, butanol and cyclohexanol; Ethers, esters and ketones such as diethyl ether, methyl tert-butyl ether, tetrahydrofuran, dioxane, dimethoxyethane, ethyl acetate, butyl acetate, butyrolactone, acetone, methyl ethyl ketone, methyl iso Butyl ketone and cyclohexanone; Carboxylic acids such as acetic acid and propionic acid; Dipolar aprotic solvents such as dimethylformamide, N-methylpyrrolidone, dimethylacetamide, sulfolane, dimethyl sulfoxide and acetonitrile; Nonpolar solvents such as toluene and xylene; Chlorinated aromatic hydrocarbons such as methylene chloride, C ₃ -C ₇ alkanes and cyclohexane.

These solvents can be used in pure form or in mixture form. In a particularly preferred embodiment of the process according to the invention, tetrahydrofuran, toluene or xylene in pure form or in the form of a mixture with the abovementioned solvents, in particular alcohols and / or C ₁ -C ₄ carboxylic acids, are used as solvents.

When using a solvent, the concentration of the aromatic nitro compound in the solution is preferably 5 to 50% by weight, in particular 10 to 30% by weight.

The reaction according to the invention is particularly preferably carried out in the liquid phase using the powdered catalyst as a catalyst for semisolid phase hydrogenation or continuously or discontinuously in a bubble column or using the shaping catalyst as a trickle bed. In addition, the reaction can be carried out in the gas phase using a powdered catalyst in the fluidized bed or using a shaped catalyst in the fixed bed.

Unsaturated carbon-carbon bonds mentioned in the present invention include alkenes, alkyne and allene bonds.

Compounds having —CN multiple bonds are, for example, oximes, imines, isocyanates, isocyanurates, hydrazones, azines and nitriles. These may be bonded directly to the aromatic moiety or may exist as substituents in the side chain. Preferred groups are nitrile, imine, oxime and hydrazone.

Compounds having —CO multiple bonds are, for example, aldehydes or ketones such as arylalkyl ketones or quinones. Such CO bonds may be directly attached to the aromatic nitro moiety or may be present in the side chain.

Such side chains may be aliphatic, cycloaliphatic, aromatic, heteroaromatic, mixed aliphatic-alicyclic, aromatic-aliphatic or heteroaromatic-aliphatic side chains.

The method is suitable when the CC- and -CN multiple bonds, carbonyl and halogen groups are present simultaneously as substituents in the complete molecule or in the side chain.

Preferably, the nitrile, oxymino, hydrazone or imine group or carbonyl group is directly bonded to the aromatic moiety of the aromatic nitro compound or may be additionally substituted by oxygen, halogen or C ₁ -C ₄ alkyl. Which may be bound via pyrazolyl, pyrimidyl or pyrimidyldione side chains.

Aromatic nitro compounds may also be substituted by additional groups of interest.

In the context of the present invention, aromatic nitro and amino compounds should be recognized as being in accordance with the Huckle 4n + 2 electron law, for example aromatic hydrocarbons such as benzene, polycyclic hydrocarbons (1, Including partially hydrogenated hydrocarbons such as 2,3,4-tetrahydronaphthalene), biphenyl, cyclopentadienyl and cycloheptatrienyl anions, anthraquinones, heteroaromatic compounds such as pyridine, pyrrole, azole , Diazines, triazines, triazoles, furans, thiophenes and oxazoles, and fused aromatic compounds such as naphthalene, anthracene, indole, quinoline, isoquinoline, carbazole, purine, phthalazine, benzotria Sol, benzofuran, cinnoline, quinazole, acridine and benzothiophene.

Such aromatic nitro compounds may contain one or more nitro groups. They preferably contain one or two nitro groups.

Preferred compound groups consist of those aromatic nitro compounds having at least one unsaturated carbon-carbon bond, in particular an alkene, alkyne or allene bond.

These compounds correspond in particular to formula (I):

Where

R ₁ is a group containing one or more unsaturated carbon-carbon bonds, —CN multiple bonds or carbonyl groups,

r is 1, 2, 3 or 4,

R ₂ is hydrogen, C ₁ -C ₁₂ alkyl, C ₁ -C ₁₂ haloalkyl, C ₁ -C ₁₂ hydroxyalkyl, C ₁ -C ₆ cyanoalkyl, C ₃ -C ₈ cycloalkyl, C ₆ -C ₁₆ aryl, C ₇ -C ₁₆ aralkyl, C ₃ -C ₆ heterocycloalkyl, C ₃ -C ₁₆ heteroaryl, C ₄ -C ₁₆ heteroaralkyl, halogen, cyano, COR ₃ , X ₁ R ₄ , -COR ₈ , ,-(O) CX _4- [CHR ₁₁ (CH ₂ ) _n1 ] Si (R ₁₂ ) ₃ , -N (R ₁₃ ) -SO ₂ -R ₁₄ , or ego,

A ₁ is cyano or -COR ₁₆ ,

R ₃ is halogen, X ₂ -R ₅ , amino, C ₁ -C ₄ alkylamino, di-C ₁ -C ₄ alkylamino, C ₂ -C ₄ haloalkylamino, di-C ₂ -C ₄ haloalkylamino , C ₁ -C ₄ alkoxyalkylamino, di-C ₁ -C ₄ alkoxyalkylamino, C ₂ -C ₄ alkenylamino, diallylamino, -N-pyrrolidino, -N-piperidino, -N -Morpholino, -N-thiomorpholino or -N-piperidazino,

R ₄ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, C ₁ -C ₄ alkylthio-C ₁ -C ₄ alkyl, di-C ₁ -C ₄ alkylamino -C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₃ -C ₇ cycloalkyl , Halo-C ₃ -C ₇ cycloalkyl, C ₁ -C ₈ alkylcarbonyl, allylcarbonyl, C ₃ -C ₇ cycloalkylcarbonyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzoyl substituted by; Furanoyl, thienyl; Phenyl, halophenyl, C ₁ -C ₄ alkylphenyl, C ₁ -C ₄ alkoxyphenyl, halo-C ₁ -C ₄ alkylphenyl, halo-C ₁ -C ₄ alkoxyphenyl, C ₁ -C ₆ alkoxycarbonyl, C ₁ -C ₄ alkoxy-C ₁ -C ₈ alkoxycarbonyl, C ₂ -C ₈ alkenyloxycarbonyl, C ₃ -C ₈ alkynyloxycarbonyl, C ₁ -C ₈ alkylthiocarbonyl, C ₂ -C ₈ alkenylthiocarbonyl, C ₃ -C ₈ alkynylthiocarbonyl, carbamoyl, mono-C ₁ -C ₄ alkylaminocarbonyl or di-C ₁ -C ₄ alkylaminocarbonyl substituted C ₁ -C ₄ alkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Phenylaminocarbonyl substituted by mono or monosubstituted by cyano; Dioxolan-2-yl unsubstituted or substituted by one or two C ₁ -C ₄ alkyl groups; Dioxan-2-yl unsubstituted or substituted by one or two C ₁ -C ₄ alkyl groups; Or C ₁ -C ₄ alkyl substituted by cyano, carboxyl or C ₁ -C ₈ alkylthio-C ₁ -C ₈ alkoxycarbonyl,

R ₅ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₁ -C ₁₀ alkylthio-C ₁ -C ₄ alkyl, Di-C ₁ -C ₄ alkylamino-C ₁ -C ₄ alkyl, cyano-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ Alkynyl, C ₃ -C ₇ cycloalkyl, C ₃ -C ₇ cycloalkyl-C ₁ -C ₄ alkyl, halo-C ₃ -C ₇ cycloalkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzyl substituted by; Alkali metal ions, alkaline earth metal ions or ammonium ions, or group [CHR ₆ (CH ₂ ) _n3 ] -COOR ₇ ,

R ₆ is hydrogen or C ₁ -C ₄ alkyl,

R ₇ is hydrogen, C ₁ -C ₆ alkyl, C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₁ -C ₈ alkoxy-C ₂ -C ₈ alkyl, C ₁ -C ₈ alkyl-thio -C ₁ -C ₈ alkyl or C ₃ -C ₇ cycloalkyl,

R ₈ and R ₂₀ are each independently hydrogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl or C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl,

R ₉ and R ₁₀ are each independently C ₁ -C ₄ alkyl, C ₂ -C ₄ haloalkyl or C ₂ -C ₈ alkoxy-alkyl,

R ₉ and R ₁₀ together form an ethano, propano or cyclo hexane-1,2-diyl bridge, these groups being unsubstituted or C ₁ -C ₄ alkyl, C ₁ -C ₄ haloalkyl or C ₁ Mono- or di-substituted by -C ₄ hydroxyalkyl,

R ₁₁ is hydrogen, C ₁ -C ₅ alkyl or C ₃ -C ₇ alkenyl,

R ₁₂ is C ₁ -C ₈ alkyl,

R ₁₃ is hydrogen, C ₁ -C ₅ alkyl, benzyl, halo-C ₁ -C ₄ alkyl, C ₂ -C ₈ alkenyl or C ₃ -C ₈ alkynyl,

R ₁₄ is C ₁ -C ₆ alkyl, halo-C ₁ -C ₅ alkyl or di-C ₁ -C ₄ alkylamino,

R ₁₅ is hydrogen, fluorine, chlorine, bromine, C ₁ -C ₄ alkyl or trifluoromethyl,

R ₁₆ is X ₃ -R ₁₇ , amino, C ₁ -C ₄ alkylamino, di-C ₁ -C ₄ alkylamino, C ₂ -C ₄ haloalkylamino, di-C ₂ -C ₄ haloalkylamino, C _1- C ₄ alkoxyalkylamino, di-C ₁ -C ₄ alkoxyalkylamino, C ₂ -C ₄ alkenylamino, diallylamino, -N-pyrrolidino, -N-piperidino, -N-mor Polyno, -N-thiomorpholino, -N-piperidazino or group -ON = C- (CH ₃ ) -CH ₃ , -O-CH ₂ -CH ₂ -ON = C (CH ₃ ) -CH ₃ or -N (OR ₂₄ ) -R ₂₂ ,

R ₁₇ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₁ -C ₁₀ alkylthio-C ₁ -C ₄ alkyl, Di-C ₁ -C ₄ alkylamino-C ₁ -C ₄ alkyl, cyano-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ Alkynyl, C ₃ -C ₇ cycloalkyl, C ₃ -C ₇ cycloalkyl-C ₁ -C ₄ alkyl, halo-C ₃ -C ₇ cycloalkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzyl substituted by; Alkali metal ions, alkaline earth metal ions or ammonium ions, or group-[CHR _25- (CH ₂ ) _m ] -COOR ₂₆ or [CHR _27- (CH ₂ ) _t Si (R ₂₃ ) ₃ ],

R ₂₂ is hydrogen or C ₁ -C ₄ alkyl,

R ₂₃ is C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl or C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl,

R ₂₄ and R ₂₅ are each independently hydrogen or C ₁ -C ₄ alkyl,

R ₂₆ is hydrogen, C ₁ -C ₆ alkyl, C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₁ -C ₈ alkoxy-C ₂ -C ₈ alkyl, C ₁ -C ₈ alkylthio- C ₁ -C ₈ alkyl or C ₃ -C ₇ cycloalkyl,

R ₂₇ is hydrogen or C ₁ -C ₄ alkyl,

m is 0, 1, 2, 3 or 4,

t is 0, 1, 2, 3 or 4,

n1, n2 and n3 are each independently 0, 1, 2, 3 or 4,

X ₁ , X ₂ , X ₃ and X ₄ are each independently oxygen or sulfur.

Preference is given to compounds of the formula (I) in which R ₁ is a group containing an unsaturated carbon-carbon bond.

In the compounds of formula (I), r is preferably 1 or 2. Particular preference is given to compounds of the formula I in which the unsaturated carbon-carbon bond of substituent R ₁ is part of the ester group.

Further preferred subgroups of compounds of formula I are compounds in which R ₂ is hydrogen, halogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy, C ₁ -C ₆ haloalkoxy or cyano, in particular R ₂ is hydrogen, It is composed of a compound which is halogen, methyl, difluoromethoxy, trifluoromethoxy or cyano.

The process according to the invention is particularly suitable for the conversion of aromatic nitro compounds of formula la to the corresponding amino compounds:

Where

R ₂ and r are as defined for Formula I,

R ₂₈ is C ₂ -C ₆ alkenyl, C ₃ -C ₆ alkynyl, C ₃ -C ₈ cycloalkenyl or C ₆ -C ₈ bicycloalkenyl,

Y ₁ is oxygen, -NH-, group Or group ego,

R ₂₉ and R ₃₀ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₂₉ and R ₃₀ together with the carbon atoms bonded thereto are one or two oxygen atoms or a group NR ₃₅ (where R ₃₅ forms a 3- to 7-membered ring which may contain hydrogen, C ₁ -C ₄ alkyl or C ₁ -C ₄ alkylcarbonyl,

R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₁ and R ₃₂ or R ₃₃ and R ₃₄ together with the carbon atom bonded thereto are one Or a 3- to 7-membered ring which may contain two oxygen atoms or a group NR ₃₆ , wherein R ₃₆ is hydrogen or C ₁ -C ₄ alkyl,

Y ₂ is oxygen, -NH-, group Or group ,

R ₃₇ and R ₃₈ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₇ and R ₃₈ together with the carbon atoms bonded thereto are one or two oxygen atoms or a group NR ₃₅ (where R ₃₅ forms a 3- to 7-membered ring which may contain hydrogen, C ₁ -C ₄ alkyl or C ₁ -C ₄ alkylcarbonyl,

R ₃₉ , R ₄₀ , R ₄₁ and R ₄₂ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₉ and R ₄₀ or R ₄₁ and R ₄₂ together with the carbon atom bonded thereto are one Or a 3- to 7-membered ring which may contain two oxygen atoms or a group NR ₄₃ , wherein R ₄₃ is hydrogen or C ₁ -C ₄ alkyl,

Z is a group Or group ,

R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ and R ₄₉ are each independently hydrogen or methyl,

p is 0 or 1,

In the compounds of formula la, preferably r is 1 or 2 and R ₂ is hydrogen, halogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy, C ₁ -C ₆ haloalkoxy or cyano.

Among the compound groups of formula la, compounds in which R ₂ is hydrogen, halogen, methyl, difluoromethoxy, trifluoromethoxy or cyano are preferred, especially compounds in which p is 1 and Y ₁ and Y ₂ are oxygen. . Particularly preferred compounds of formula (Ia) in this group are those in which Z is a group Wherein R ₄₄ and R ₄₅ are preferably methyl.

Further subgroups of compounds of formula I correspond to formula Ib:

Where

Y ₁ , Y ₂ , Z, p and R ₂₈ are as defined for Formula Ia,

R ₅₀ is hydrogen or halogen,

R ₅₁ is hydrogen, halogen, methyl, difluoromethoxy, trifluoromethoxy or cyano,

Preferably R ₅₀ is hydrogen, R ₅₁ is chlorine and R ₂₈ is allyl.

If the compound of formula (I) has an asymmetric center, the compound may exist in optical isomeric form. Some compounds of formula I may exist in tautomeric forms (eg, keto-enol tautomers). If aliphatic C═C double bonds are present, geometric isomers may be present (E form or Z form). Moreover, exo-endo coordination is also possible. Formula I includes all possible stereoisomers which exist in the form of enantiomers, tautomers, diastereomers, E / Z isomers or mixtures thereof.

In the above definition, halogen should be recognized as being fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.

Alkyl is methyl, ethyl, isopropyl, n-propyl, n-butyl, iso-butyl, secondary-butyl, tert-butyl, or pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl radicals Are various isomers.

Haloalkyl is, for example, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, trichloromethyl, 2,2,2-trifluoroethyl, 2-fluoroethyl, 2 -Chloroethyl or 2,2,2-trichloroethyl, preferably trichloromethyl, difluorochloromethyl, trifluoromethyl or dichlorofluoromethyl.

Alkoxy is, for example, methoxy, ethoxy, propyloxy, iso-propyloxy, n-butyloxy, iso-butyloxy, secondary-butyloxy or tert-butyloxy, preferably methoxy or Oxy.

Haloalkoxy is, for example, fluoromethoxy, difluoromethoxy, trifluoromethoxy, 2,2,2-trifluoroethoxy, 1,1,2,2-tetrafluoroethoxy, 2- Fluoroethoxy, 2-chloroethoxy or 2,2,2-trichloroethoxy, preferably difluoromethoxy, 2-chloroethoxy or trifluoromethoxy.

Alkylthio is, for example, isomer of methylthio, ethylthio, propylthio, isopropylthio, n-butylthio, iso-butylthio, secondary-butylthio, tert-butylthio, or pentylthio, preferably Preferably methylthio or ethylthio.

Alkenyl is recognized as being straight or branched alkenyl, for example vinyl, allyl, metallyl, 1-methylvinyl, but-2-en-1-yl, pentenyl, 2-hexenyl or 3-heptenyl Should be.

Preference is given to alkenyl radicals having a chain length of 2 or 3 carbon atoms. The olefinic double bond may be mono-, di-, tri- or tetra-substituted.

The alkynyl radicals appearing in the definition of the substituents may be straight or branched chains, for example propargyl, 3-butynyl, 1-methylpropargyl, 1-pentynyl or 2-hexynyl. Such alkyne functional groups can be mono- or disubstituted.

Cycloalkyl is, for example, cyclopropyl, dimethylcyclopropyl, cyclobutyl, cyclopentyl, methyl-cyclopentyl, cyclohexyl or cycloheptyl, preferably cyclopropyl, cyclopentyl or cyclohexyl.

Alkoxycarbonyl is, for example, methoxycarbonyl, ethoxycarbonyl, n-propyloxycarbonyl, iso-propyloxycarbonyl or n-butyloxycarbonyl, preferably methoxycarbonyl or ethoxy Carbonyl.

Alkoxyalkyl is, for example, methoxymethyl, ethoxymethyl, propyloxymethyl, methoxyethyl, ethoxyethyl, propyloxyethyl, methoxypropyl, ethoxypropyl or propyloxypropyl.

Alkylthioalkyl is, for example, methylthiomethyl, ethylthiomethyl, methylthioethyl, ethylthioethyl or isopropylthioethyl.

Alkylaminoalkyl is, for example, methylaminoethyl, dimethylaminoethyl, ethylaminoethyl or diethylaminoethyl.

Cyanoalkyl is, for example, cyanomethyl, cyanoethyl or cyanopropyl.

Halocycloalkyl is, for example, 2,2-dichlorocyclopropyl or pentachlorocyclohexyl.

Alkylsulfonyl is, for example, methylsulfonyl, ethylsulfonyl, propylsulfonyl or butylsulfonyl. Methyl- and ethyl-sulfonyl are preferred.

Phenyl, which is included as part of substituents such as phenoxy, phenylthio, phenoxy carbonyl, phenylaminocarbonyl, benzyl or benzoyl, may be present in an unsubstituted form or in a form substituted by further substituents. . Such substituents may be in ortho, meta and / or para positions. Ortho and para positions relative to the ring linking site are preferred substituent positions. Halogen atoms are preferred substituents.

Aralkyl is, for example, benzyl, phenethyl, 3-phenylpropyl, α-methylbenzyl, phenbutyl or α, α-dimethylbenzyl.

Aryl is, for example, phenyl, 1,2,3,4-tetrahydronaphthalene, indene, naphthalene, azulene or anthracene.

Heteroaryl is, for example, pyrrole, furan, thiophene, oxazole, thiazole, pyridine, pyrazine, pyrimidine, pyridazine, indole, purine, quinoline or isoquinoline.

Heterocycloalkyl is, for example, oxirane, oxetane, azetidine, aziline, 1,2-oxathiolane, pyrazoline, pyrrolidine, piperidine, piperazine, morpholine, dioxolane, tetrahydro Pyran, tetrahydrofuran or tetrahydrothiophene.

Specific examples of particularly preferred individual compounds of formula (Ic) that can be hydrogenated with compounds of formula (Id) are listed in Table 1:

The position of the substituents is based on the nitro group in the 1-position.

Compound number R _a R _b R _c 101 3-COO-C (CH ₃ ) ₂ COO-CH ₂ -CH = CH ₂ 4-Cl H 102 3-OCH ₂ -C≡CH 4-O-CH ₂ -C≡CH 5-Cl 103 4-O-CH ₂ -C≡CH 3-CONH-C ₁ -C ₁₂ alkyl H 104 3-SCH ₂ CH = CH-CH = CCl ₂ 6-NH ₂ H 105 3-NO ₂ -COOC ₂ H ₄ OCOC (CH ₃ ) ₂ = CH ₂ H 106 3-OCH ₂ CH = CH ₂ H H 107 3-NO ₂ 4-C≡CH H 108 3-CH = CH ₂ H H 109 3-C≡CC (CH ₃ ) ₃ H H

The present invention also relates to the use of phosphorus-modified noble metal catalysts for catalytic hydrogenation of substituted aromatic nitro compounds containing at least one carbon-carbon, carbon-nitrogen or carbon-oxygen multiple bond in an aromatic moiety or side chain. will be.

The following examples are intended to illustrate the invention.

Example A1: Impregnation of Activated Carbon with Ammonium Vanadate

300 mg of ammonium vanadate is placed in a vessel with agitator with 600 ml of deionized water. 20 g of activated carbon are then added thereto and the mixture is stirred for 30 minutes. The impregnated activated carbon is then filtered and washed with 600 ml of deionized water in several portions. Finally, the vanadium containing carbon is dried to a constant weight in a vacuum drying cabinet at 60 ° C. 18.8 g of modified carbon having a vanadium content of 13.6 mg / g are obtained.

Example B: Hydrogenation

Example B1 Preparation of 2- (2-Chloro-5-amino-benzoyloxy) -2-methyl-propionic acid allyl ester

0.9 g of vanadium-containing activated carbon prepared according to Example A1 is added to a solution of 16.1 g of 2- (2-chloro-5-nitrobenzoyloxy) -2-methyl propionic acid allyl ester and 100 mg of toluene in an autoclave with a stirrer. . 82 mg of the platinum-carbon catalyst is placed in a separate glass vessel with 50 mg of hypophosphoric acid and 2 ml of deionized water and the mixture is stirred for 10 minutes. While the glass vessel is washed with 4 ml of deionized water, the catalyst suspension is transferred to an autoclave and hydrogenated at a temperature of 100 ° C. and hydrogen pressure of 20 bar for 2 hours. After cooling and making the autoclave inert with nitrogen, the catalyst is filtered off and washed with 20 ml of toluene. After working up by distillation, 14 g of 2- (2-chloro-5-amino-benzoyloxy) -2-methyl-propionic acid allyl ester having a content of 98.9% were obtained according to HPLC (yield: 94.8% of theory). ¹ H-NMR (CDCl ₃ , 250 MHz) 1.62 ppm (s, 6H); 3.65 ppm (s, 2H); 4.6 ppm (d, 2H); 5.2 ppm (q, 2H); 5.85 ppm (m, 1 H); 6.65 ppm (m, 1 H); 7.0 ppm (m, 1H); 7.1 ppm (m, 1 H).

Example B2-B5

The procedure is as described in Example B1 and the amino compounds mentioned in Table 2 are obtained from the corresponding nitro compounds.

Example B6 Preparation of 2- (2-Chloro-5-amino-benzoyloxy) -2-methyl-propionic acid allyl ester

5.9 kg of 5% Pt / C catalyst 5% (H ₂ O content: 62.8%) is placed in a 60 liter steel container with 12 liters of water and a 50% H ₃ PO ₂ solution (= 5% phosphorus based on catalyst) ) Add 470 g. After stirring the catalyst slurry for 10 minutes at room temperature, 360 g (0.2 mol%) of vanadilacetylacetonate VO (acac) ₂ is added and the mixture is stirred for an additional 5 minutes. 550 kg (content: 40%, 0.67 kmol) of a solution of 2- (chloro-5-nitro-benzoyloxy) -2-methyl-propionic acid allyl ester in toluene are placed in an autoclave with a stirrer and the steel vessel is placed in 15 kg of water. The catalyst suspension is added while washing. It is then hydrogenated for 2 hours at a temperature of 100 ° C. and a hydrogen pressure of 5 bar. After cooling and making the autoclave inert with nitrogen, the catalyst is filtered at 50 ° C. and washed with 50 kg of toluene. After distillation to work up, 196 kg of 2- (chloro-5-amino-benzoyloxy) -2-methyl-propionic acid allyl ester are obtained (yield: 98% of theory). The over-hydrogenated propyl ester content is <0.05%. ¹ H-NMR (CDCl ₃ , 250 MHz) 1.62 ppm (s, 6H); 3.65 ppm (s, 2H); 4.6 ppm (d, 2H); 5.2 ppm (q, 2H); 5.85 ppm (m, 1 H); 6.65 ppm (m, 1 H); 7.0 ppm (m, 1H); 7.1 ppm (m, 1 H).

Claims (42)

The corresponding substituted aromatic nitro compounds are catalytically hydrogenated in the presence of noble metal catalysts of rhodium, ruthenium, iridium, platinum or palladium modified with inorganic or organophosphorus compounds having an oxidation state of less than 5, thereby carbon-carbon in the aromatic moiety or side chain. To prepare substituted aromatic amino compounds containing at least one carbon-nitrogen or carbon-oxygen multiple bond. The process of claim 1 wherein platinum or palladium is used as the noble metal catalyst. The method of claim 1 wherein platinum is used as the noble metal catalyst. The process according to claim 1, wherein the noble metal catalyst is used in an amount of 0.1 to 10% by weight based on the aromatic nitro compound used. The process according to claim 1, wherein the noble metal catalyst is used in an amount of 0.5 to 2% by weight based on the aromatic nitro compound used. 4. The process of claim 3 wherein the noble metal catalyst used in the reforming process is applied to the carrier in metal form or in oxidized form. The method of claim 6, wherein the carrier is activated carbon, silicon dioxide in the form of silicic acid, silica gel, aluminum oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate, titanium oxide, magnesium oxide, iron oxide, lead oxide, lead sulfate or carbonic acid. How to pay. 8. The method of claim 7, wherein the carrier is activated carbon, aluminum oxide or silicon dioxide. The process of claim 6 wherein the noble metal catalyst contains 1 to 10 weight percent platinum. The modified phosphorus compound according to claim 1, wherein the phosphorus compound for modification is phosphine P (R _a ) _3-n (H) _n , phosphinoic acid HO-P (H) _m (R _a ) _2-m , phosphine oxide O = P (R _a ) _3-n (H) _n , hypophosphonoic acid And , Hypophosphoric acid O = P (OH) (H) _m (R _a ) _2-m and phosphoric acid O = P (OH) ₂ H and O = P (OH) ₂ R _a , wherein R _a is straight or branched chain C ₁ -C ₁₂ alkyl, C ₆ -C ₁₆ aryl or C ₄ -C ₁₆ heteroaryl, m is 0, 1 or 2 and n is 0, 1, 2 or 3). A diphenylphosphine, triphenylphosphine, phosphinoic acid or salt thereof, amide or ester, diphenylphosphinic acid, diphenyl phosphite, phosphine oxide, phosphoric acid or a salt or ester thereof, or hypo Phosphoric acid or salts or esters thereof is used as the phosphorus compound for modification. 12. The process of claim 11 wherein phosphoric acid or a salt or ester thereof, or hypophosphoric acid or a salt or ester thereof is used as the phosphorus compound for modification. The process of claim 1 wherein the process of modifying the noble metal catalyst with a phosphorus compound is carried out in situ prior to the hydrogenation process. The process of claim 1 wherein the ratio of noble metal catalyst to phosphorus compound for reforming is from 1: 0.1 to 1: 1000 parts by weight. The process of claim 1 wherein the ratio of the noble metal catalyst to the modifying phosphorus compound is from 1: 5 to 1: 200 parts by weight. The process of claim 1 wherein Fe ²⁺ , Fe ³⁺ , Ru ³⁺ , Mn ²⁺ , Mn ³⁺ , Co ²⁺ , Co ³⁺ , or a vanadium compound, wherein vanadium is in an oxidized state of 0, II, III, Transition metal ions from IV or V) as a promoter. 17. The method of claim 16, wherein a vanadium compound in which the oxidation state of vanadium is 0, II, III, IV or V is added as a promoter. 18. The process of claim 17, wherein the vanadium compound is dissolved or dispersed in a catalytic amount in the reaction medium. 18. The process of claim 17, wherein the vanadium compound is first applied to a suitable carrier material and then dispersed in the reaction medium in this form. 18. The vanadium compound of claim 17, wherein the vanadium compound is vanadium (III) acetylacetonate, vanadium (IV) oxyacetylacetonate, V ₂ O ₅ , VOCl ₃ , VCl ₆ ⁻ , [VO (SCN) ₄ ] ^2- , VOSO ₄ , NH ₄ VO ₃ , LiVO ₃ , NaVO ₃ , KVO ₃ , VCl ₃ , VCl ₂ , and the corresponding halide group with F or Br. The method of claim 20 wherein ammonium, lithium, sodium or potassium vanadate, or a hydrate of these vanadates is used. 21. The method of claim 20, wherein vanadium (III) acetylacetonate or vanadium (IV) oxyacetylacetonate is used. The process of claim 1 wherein the vanadium compound is used in an amount of 1 to 2000 ppm based on the aromatic nitro compound to be hydrogenated. The method of claim 23, wherein the vanadium compound is used in an amount of 5 to 1000 ppm based on the aromatic nitro compound to be hydrogenated. The process of claim 1 wherein the weight ratio of vanadium compound to noble metal catalyst is from 1: 1 to 1: 10,000. The method of claim 25, wherein the weight ratio of vanadium compound to noble metal catalyst is from 1:50 to 1: 750. The process of claim 1 which is carried out under pressure of 1 to 100 bar. The method of claim 27, wherein the process is performed under pressure of 1 to 40 bar. The method of claim 1 wherein the temperature is 0 to + 160 ° C. 3. The method of claim 29, wherein the temperature is from +20 to + 100 ° C. 30. The process of claim 1 wherein the hydrogenation process is carried out without solvent if the compound to be hydrogenated is a liquid at reaction temperature. The method of claim 1 wherein tetrahydrofuran, toluene or xylene is used as the solvent. The method of claim 1, wherein the aromatic nitro compound has one or more unsaturated carbon-carbon bonds. The method of claim 1 wherein the compound corresponds to formula (I). Formula I Where R ₁ is a group containing one or more unsaturated carbon-carbon bonds, —CN multiple bonds or carbonyl groups, r is 1, 2, 3 or 4, R ₂ is hydrogen, C ₁ -C ₁₂ alkyl, C ₁ -C ₁₂ haloalkyl, C ₁ -C ₁₂ hydroxyalkyl, C ₁ -C ₆ cyanoalkyl, C ₃ -C ₈ cycloalkyl, C ₆ -C ₁₆ aryl, C ₇ -C ₁₆ aralkyl, C ₃ -C ₆ heterocycloalkyl, C ₃ -C ₁₆ heteroaryl, C ₄ -C ₁₆ heteroaralkyl, halogen, cyano, COR ₃ , X ₁ R ₄ , -COR ₈ , ,-(O) CX _4- [CHR ₁₁ (CH ₂ ) _n1 ] Si (R ₁₂ ) ₃ , -N (R ₁₃ ) -SO ₂ -R ₁₄ , or ego, A ₁ is cyano or -COR ₁₆ , R ₃ is halogen, X ₂ -R ₅ , amino, C ₁ -C ₄ alkylamino, di-C ₁ -C ₄ alkylamino, C ₂ -C ₄ haloalkylamino, di-C ₂ -C ₄ haloalkylamino , C ₁ -C ₄ alkoxyalkylamino, di-C ₁ -C ₄ alkoxyalkylamino, C ₂ -C ₄ alkenylamino, diallylamino, -N-pyrrolidino, -N-piperidino, -N -Morpholino, -N-thiomorpholino or -N-piperidazino, R ₄ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, C ₁ -C ₄ alkylthio-C ₁ -C ₄ alkyl, di-C ₁ -C ₄ alkylamino -C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₃ -C ₇ cycloalkyl , Halo-C ₃ -C ₇ cycloalkyl, C ₁ -C ₈ alkylcarbonyl, allylcarbonyl, C ₃ -C ₇ cycloalkylcarbonyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzoyl substituted by; Furanoyl, thienyl; Phenyl, halophenyl, C ₁ -C ₄ alkylphenyl, C ₁ -C ₄ alkoxyphenyl, halo-C ₁ -C ₄ alkylphenyl, halo-C ₁ -C ₄ alkoxyphenyl, C ₁ -C ₆ alkoxycarbonyl, C ₁ -C ₄ alkoxy-C ₁ -C ₈ alkoxycarbonyl, C ₂ -C ₈ alkenyloxycarbonyl, C ₃ -C ₈ alkynyloxycarbonyl, C ₁ -C ₈ alkylthiocarbonyl, C ₂ -C ₈ alkenylthiocarbonyl, C ₃ -C ₈ alkynylthiocarbonyl, carbamoyl, mono-C ₁ -C ₄ alkylaminocarbonyl or di-C ₁ -C ₄ alkylaminocarbonyl substituted C ₁ -C ₄ alkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Phenylaminocarbonyl substituted by mono or monosubstituted by cyano; Dioxolan-2-yl unsubstituted or substituted by one or two C ₁ -C ₄ alkyl groups; Dioxan-2-yl unsubstituted or substituted by one or two C ₁ -C ₄ alkyl groups; Or C ₁ -C ₄ alkyl substituted by cyano, carboxyl or C ₁ -C ₈ alkylthio-C ₁ -C ₈ alkoxycarbonyl, R ₅ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₁ -C ₁₀ alkylthio-C ₁ -C ₄ alkyl, Di-C ₁ -C ₄ alkylamino-C ₁ -C ₄ alkyl, cyano-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ Alkynyl, C ₃ -C ₇ cycloalkyl, C ₃ -C ₇ cycloalkyl-C ₁ -C ₄ alkyl, halo-C ₃ -C ₇ cycloalkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzyl substituted by; Alkali metal ions, alkaline earth metal ions or ammonium ions, or group [CHR ₆ (CH ₂ ) _n3 ] -COOR ₇ , R ₆ is hydrogen or C ₁ -C ₄ alkyl, R ₇ is hydrogen, C ₁ -C ₆ alkyl, C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₁ -C ₈ alkoxy-C ₂ -C ₈ alkyl, C ₁ -C ₈ alkyl-thio -C ₁ -C ₈ alkyl or C ₃ -C ₇ cycloalkyl, R ₈ and R ₂₀ are each independently hydrogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl or C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, R ₉ and R ₁₀ are each independently C ₁ -C ₄ alkyl, C ₂ -C ₄ haloalkyl or C ₂ -C ₈ alkoxy-alkyl, R ₉ and R ₁₀ together form an ethano, propano or cyclohexane-1,2-diyl bridge and these groups are unsubstituted or C ₁ -C ₄ alkyl, C ₁ -C ₄ haloalkyl or C ₁ Mono- or di-substituted by -C ₄ hydroxyalkyl, R ₁₁ is hydrogen, C ₁ -C ₅ alkyl or C ₃ -C ₇ alkenyl, R ₁₂ is C ₁ -C ₈ alkyl, R ₁₃ is hydrogen, C ₁ -C ₅ alkyl, benzyl, halo-C ₁ -C ₄ alkyl, C ₂ -C ₈ alkenyl or C ₃ -C ₈ alkynyl, R ₁₄ is C ₁ -C ₆ alkyl, halo-C ₁ -C ₅ alkyl or di-C ₁ -C ₄ alkylamino, R ₁₅ is hydrogen, fluorine, chlorine, bromine, C ₁ -C ₄ alkyl or trifluoromethyl, R ₁₆ is X ₃ -R ₁₇ , amino, C ₁ -C ₄ alkylamino, di-C ₁ -C ₄ alkylamino, C ₂ -C ₄ haloalkylamino, di-C ₂ -C ₄ haloalkylamino, C _1- C ₄ alkoxyalkylamino, di-C ₁ -C ₄ alkoxyalkylamino, C ₂ -C ₄ alkenylamino, diallylamino, -N-pyrrolidino, -N-piperidino, -N-mor Polyno, -N-thiomorpholino, -N-piperidazino or group -ON = C- (CH ₃ ) -CH ₃ , -O-CH ₂ -CH ₂ -ON = C (CH ₃ ) -CH ₃ or -N (OR ₂₄ ) -R ₂₂ , R ₁₇ is hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, halo-C ₁ -C ₈ alkyl, C ₁ -C ₁₀ alkylthio-C ₁ -C ₄ alkyl, Di-C ₁ -C ₄ alkylamino-C ₁ -C ₄ alkyl, cyano-C ₁ -C ₈ alkyl, C ₂ -C ₈ alkenyl, halo-C ₂ -C ₈ alkenyl, C ₃ -C ₈ Alkynyl, C ₃ -C ₇ cycloalkyl, C ₃ -C ₇ cycloalkyl-C ₁ -C ₄ alkyl, halo-C ₃ -C ₇ cycloalkyl; Unsubstituted or substituted on up to 3 identical or different substituents selected from halogen, C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkoxy and C ₁ -C ₄ alkoxy on the phenyl ring Benzyl substituted by; Alkali metal ions, alkaline earth metal ions or ammonium ions, or group-[CHR _25- (CH ₂ ) _m ] -COOR ₂₆ or [CHR _27- (CH ₂ ) _t Si (R ₂₃ ) ₃ ], R ₂₂ is hydrogen or C ₁ -C ₄ alkyl, R ₂₃ is C ₁ -C ₄ alkyl, halo-C ₁ -C ₄ alkyl or C ₁ -C ₄ alkoxy-C ₁ -C ₄ alkyl, R ₂₄ and R ₂₅ are each independently hydrogen or C ₁ -C ₄ alkyl, R ₂₆ is hydrogen, C ₁ -C ₆ alkyl, C ₂ -C ₈ alkenyl, C ₃ -C ₈ alkynyl, C ₁ -C ₈ alkoxy-C ₂ -C ₈ alkyl, C ₁ -C ₈ alkylthio- C ₁ -C ₈ alkyl or C ₃ -C ₇ cycloalkyl, R ₂₇ is hydrogen or C ₁ -C ₄ alkyl, m is 0, 1, 2, 3 or 4, t is 0, 1, 2, 3 or 4, n1, n2 and n3 are each independently 0, 1, 2, 3 or 4, X ₁ , X ₂ , X ₃ and X ₄ are each independently oxygen or sulfur. The method of claim 34, wherein R ₁ in the compound of Formula I is a group containing an unsaturated carbon-carbon bond. 35. The method of claim 34, wherein r is 1 or 2 in the compound of formula (I). The method of claim 34, wherein R ₂ in the compound of formula I is hydrogen, halogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy, C ₁ -C ₆ haloalkoxy or cyano. 35. The method of claim 34, wherein the aromatic nitro compound of formula la is hydrogenated to the corresponding amino compound. Formula Ia Where R ₂ and r are as defined in claim 34, R ₂₈ is C ₂ -C ₆ alkenyl, C ₃ -C ₆ alkynyl, C ₃ -C ₈ cycloalkenyl or C ₆ -C ₈ bicycloalkenyl, Y ₁ is oxygen, -NH-, group Or group ego, R ₂₉ and R ₃₀ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₂₉ and R ₃₀ together with one or two oxygen atoms or groups NR ₃₅ (wherein R ₃₅ together with the carbon atoms bonded thereto) Forms a 3- to 7-membered ring which may contain hydrogen, C ₁ -C ₄ alkyl or C ₁ -C ₄ alkylcarbonyl, R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₁ and R ₃₂ or R ₃₃ and R ₃₄ together with one or more carbon atoms bonded thereto are To form a three to seven membered ring which may contain two oxygen atoms or a group NR ₃₆ , wherein R ₃₆ is hydrogen or C ₁ -C ₄ alkyl, Y ₂ is oxygen, -NH-, group Or group , R ₃₇ and R ₃₈ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₇ and R ₃₈ together with the carbon atoms bonded thereto are one or two oxygen atoms or a group NR ₃₅ (wherein R ₃₅ Forms a 3- to 7-membered ring which may contain hydrogen, C ₁ -C ₄ alkyl or C ₁ -C ₄ alkylcarbonyl, R ₃₉ , R ₄₀ , R ₄₁ and R ₄₂ are each independently hydrogen or C ₁ -C ₄ alkyl, or R ₃₉ and R ₄₀ or R ₄₁ and R ₄₂ together with one or more carbon atoms bonded thereto To form a 3- to 7-membered ring which may contain two oxygen atoms or a group NR ₄₃ , wherein R ₄₃ is hydrogen or C ₁ -C ₄ alkyl, Z is a group Or group , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ and R ₄₉ are each independently hydrogen or methyl, p is 0 or 1, In the compound of formula la, preferably r is 1 or 2 and R ₂ is hydrogen, halogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy, C ₁ -C ₆ haloalkoxy or cyano. 38. The process of claim 37, wherein in the compound of formula la, R ₂ is hydrogen, halogen, methyl, difluoromethoxy, trifluoromethoxy or cyano, in particular p is 1 and Y ₁ and Y ₂ are oxygen. The compound of claim 37, wherein in the compound of formula la, Z is a group Wherein R ₄₄ and R ₄₅ are methyl. The method of claim 34, wherein the compound corresponds to Formula Ib. Formula Ib Where Y ₁ , Y ₂ , Z, p and R ₂₈ are as defined for Formula Ia in claim 37, R ₅₀ is hydrogen or halogen, R ₅₁ is hydrogen, halogen, methyl, difluoromethoxy, trifluoromethoxy or cyano. Use of the modified noble metal catalyst according to claim 1 for catalytic hydrogenation of a substituted aromatic nitro compound containing at least one carbon-carbon, carbon-nitrogen or carbon-oxygen multiple bond in an aromatic moiety or side chain.